Activity for the week of 16 July-22 July 2008

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.

New Activity / Unrest

On 21 July, AVO raised the Volcano Alert Level for Cleveland to Watch and the Aviation Color Code to Orange based on reports from pilots and observers on fishing boats. Reports from fishing boats indicated that an eruption started at about 1200 and ash near sea level may have drifted NW. Pilots reported that an ash-and-steam plume rose to altitudes of 4.6-5.2 km (15,000-17,000 ft) a.s.l. and drifted SE. Observations of satellite imagery on 22 July revealed a steam plume possibly containing some ash drifting more than 50 km ESE at altitudes of 3-6.1 km (10,000-20,000 ft) a.s.l. A strong thermal anomaly interpreted as a possible lava flow was also present in the imagery.

Based on a pilot report and inconclusive observations of satellite imagery, the Darwin VAAC reported that on 17 July a possible ash plume from Galunggung rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted SW. CVGHM did not report eruptive activity and advised that the activity status was "normal."

SERNAGEOMIN reported that after increased seismicity at Llaima on 14 July, an ash plume rose to an altitude of 5.6 km (18,400 ft) a.s.l. Less than two hours later, very intense orange and red incandescence was seen through breaks in the cloud cover near the summit and at the base of the W flank. At 1915 a vigorous Strombolian eruption ejected incandescent pyroclastic material from the N vent in the main crater to heights of 500 m above the summit. Seismicity and the intensity of the explosions decreased later that day. On 15 July, diffuse ash emissions rose to an altitude of 3.4 km (11,200 ft) a.s.l. Ash and tephra covered areas of the SSE flank. Seismic activity decreased during 16-18 July.

On 19 July, seismicity again increased and ash-and-gas plumes rose to an altitude of 3.3 km (10,800 ft) a.s.l. and drifted SE. The emissions became more intense and frequent, and one explosion produced an ash plume to an altitude of 4.1 km (13,500 ft) a.s.l. Ash and tephra fell on the SE flank. Later that day, constant explosions ejected incandescent material 500 m above the summit that fell near the crater. Steam plumes emitted from the W flank possibly indicated the presence of a new lava flow along with mobile incandescent blocks from a previous lava flow. After another brief period of calm, vapor emissions increased and were followed by strong explosions and lava flows. The Alert level remained at Yellow.

AVO reported that during 15-16 July seismicity from Okmok changed from nearly continuous to episodic volcanic tremor, and the overall seismic intensity declined. Satellite imagery indicated elevated surface temperatures in the NE sector of the caldera; meteorological clouds obscured views. On 16 July, the Volcano Alert Level was lowered to Watch and the Aviation Color Code was lowered to Orange. On 17 July, a pilot reported that an ash plume rose to altitudes of 4.6-6.1 km (15,000-20,000) a.s.l. and drifted E and NE. On 18 July, AVO indicated that the eruption was episodic, with occasional ash-producing explosions occurring every 15 to 30 minutes. The plumes from these explosions were limited to about 6.1 km (20,000 ft) a.s.l.

On 19 July seismicity increased markedly, interpreted as possibly indicating that ash plumes rose to altitudes of 7.6-9.1 km (25,000-30,000 ft) a.s.l. The Volcano Alert Level was raised to Warning and the Aviation Color Code was raised to Red. The next day, seismicity declined again and the Volcano Alert Level was lowered to Watch and the Aviation Color Code was lowered to Orange. Satellite imagery revealed that an ash plume about 20 km from Okmok drifted SE at an altitude of 3.7 km (12,000 ft) a.s.l. Additional ash plumes observed on satellite imagery and spotted by pilots rose to altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. During 21-22 July, ash plumes rose to altitudes of 6.1-9.1 km (20,000-30,000 ft) a.s.l. and drifted SE.

Ongoing Activity

Based on observations of satellite imagery, the Darwin VAAC reported that during 16-18 July ash plumes from Batu Tara rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted W. A thermal anomaly was noted on satellite imagery on 16 July.

KVERT reported that intermittent volcanic tremor at Bezymianny was detected on 11 July and seismic activity was above background levels during 11-16 July. Weak thermal anomalies over the lava dome were detected in satellite imagery on 11 and 15 July. Hot avalanches were reported by local observers on 15 July. The level of Concern Color Code remained at Orange.

SERNAGEOMIN reported that after two weeks of inclement weather around Chaitén, clouds cleared on 18 July and ash plumes were observed. During 18-21 July mushroom-shaped ash plumes emitted from the S sector of the new lava dome rose to an altitude of 2.5 km (8,200 ft) a.s.l. Occasionally, explosions would push the plumes to altitudes of 3 km (10,000 ft) a.s.l. The plumes drifted N and NW, affecting several areas on the coast. The Alert Level remained at Red.

INGV-CT reported that an inspection of Etna's summit craters on 15 July revealed degassing from the Northeast Crater and to a lesser degree from the BN-1 crater of the Bocca Nuova. Explosive activity was restricted to Vent 2 of the active NW-SE-trending fissure E of the summit craters and characterized by weak Strombolian activity and diffuse ash emissions. During 15 and 17 July lava flows were active in the Valle del Bove. On 17 July, no explosive activity was seen along the fissure.

Based on visual observations from HVO crews, video footage, pilot reports, and web camera views, HVO reported that during 16-22 July, lava flowed SE through a lava tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex. The lava flowed into the ocean at the Waikupanaha ocean entry resulting in occasional explosions and a vigorous steam plume from contact with the water. Lightning was sometimes seen in the steam plume. Incandescence was observed from the TEB vent, rootless shields, breakouts along the W margin of the TEB lava tube, and from vents and sporadic spatter in Pu'u 'O'o crater. The sulfur dioxide emission rate at Pu'u 'O'o was very high at 6,300 tonnes per day on 17 July; the average background rate is about 2,000 tonnes per day.

During the reporting period, Kilauea earthquakes were located beneath the summit area and beneath Halema'uma'u crater, along S-flank faults, and along the E and SW rift zones. Beneath Halema'uma'u crater, another 20-40 small earthquakes per day also occurred but were too small to be located. The vent in the crater continued to produce a white plume with minor ash content that drifted mainly SW. Night-time incandescence was seen at the base of the plume. Rock clattering, booming noises, and "rushing sounds" were heard in the vicinity of Halema'uma'u crater. The sulfur dioxide emission rate was high and between 700 and 800 tonnes per day, during 16-18 July. The pre-2008 background rate was 150-200 tonnes per day. On 19 July, incandescent material was ejected from the vent.

INSIVUMEH reported that during 9-16 July, Strombolian activity from Pacaya's MacKenney cone was mainly characterized by explosions approximately 2-3 minutes apart. Pyroclastic material was ejected about 25 m above the crater. Lava flowed 100-200 m down the NW flank and continued to slowly fill in the area between MacKenney cone and Cerro Chino crater to the N. On 16 July, fumarolic plumes drifted SW.

KVERT reported that seismic activity at Shiveluch was slightly above background levels during 11-18 July and possibly indicated ash explosions up to 4.5 km (14,800 ft) a.s.l. on 17 July. Moderate fumarolic activity was seen on 13 and 15 July. Observations of satellite imagery revealed a thermal anomaly on the lava dome during 10-11 and 13-17 July. The Level of Concern Color Code remained at Orange.

MVO reported no evidence of lava-dome growth at Soufrière Hills during 11-18 July. Seismic activity remained low. The E talus slope continued to erode, producing minor rockfalls that descended into the Tar River Valley. Following a small swarm of volcano-tectonic earthquakes on 20 July, four eruptive events each produced ash plumes that rose to altitudes of 2 km (6,000 ft) a.s.l. and drifted W. The first two events generated plumes above the Tar River Valley possibly from small pyroclastic flows. Ashfall was reported in Old Towne. Rumbling noises were heard in nearby areas and lightning strikes were observed. The Alert Level remained elevated at 4 (on a scale of 0-5).

On 10 July, CVO lowered the Volcano Alert Level for Mount St. Helens to Normal and the Aviation Color Code to Green, following the cessation of lava-dome growth in late January and about five months with no signs of renewed activity. Earthquakes, volcanic gas emissions, and ground deformation were all at pre-eruptive background levels.

The IG reported that during 15-22 July, explosions from Tungurahua were detected by the seismic network. Although clouds occasionally inhibited visual observations, steam and ash-and-steam plumes were spotted and rose to altitudes of 7-10 km (23,000-32,800 ft) a.s.l. and drifted W and SW. On 19 and 22 July, nighttime incandescence from the crater was observed. On 20 July, lahars descended NW and S drainages. Ashfall was reported in areas downwind during 19-22 July. On 21 and 22 July, explosions vibrated windows in areas NW.

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Criteria & Disclaimers

Criteria

The Weekly Volcanic Activity Report does not necessarily include all volcanic activity that occurred on Earth during the week. More than a dozen volcanoes globally have displayed more-or-less continuous eruptive activity for decades or longer, and such routine activity is typically not reported here. Moreover, Earth's sea-floor volcanism is seldom reported even though in theory it represents the single most prolific source of erupted material. The Weekly Volcanic Activity Report summarizes volcanic activity that meets one or more of the following criteria:

- A volcano observatory raises or lowers the alert level at the volcano.
- A volcanic ash advisory has been released by a volcanic ash advisory center (VAAC) stating that an ash cloud has been produced from the volcano.
- A verifiable news report of new activity or a change in activity at the volcano has been issued.
- Observers have reported a significant change in volcanic activity. Such activity can include, but is not restricted to, pyroclastic flows, lahars, lava flows, dome collapse, or increased unrest.

Volcanoes are included in the "New Activity/Unrest" section of the Weekly Volcanic Activity Report if the activity occurs after at least 3 months of quiescence. Once a volcano is included in the "New Activity/Unrest" section, updates will remain in that section unless the activity continues for more than 1 month without escalating, after which time updates will be listed in the "Continuing Activity" section. Volcanoes are also included in the "New Activity/Unrest" section if the volcano is undergoing a period of relatively high unrest, or increasing unrest. This is commonly equal to Alert Level Orange on a scale of Green, Yellow, Orange, Red, where Red is the highest alert. Or alert level 3 on a scale of 1-4 or 1-5.

It is important to note that volcanic activity meeting one or more of these criteria may occur during the week, but may not be included in the Weekly Volcanic Activity Report because we did not receive a report.

Disclaimers

1. The Weekly Volcanic Activity Report is intended to provide timely information about global volcanism on a weekly basis. Consequently, the report is generated rapidly by summarizing volcanic reports from various sources, with little time for fact checking. The accuracy of the Weekly Volcanic Activity Report is dependent upon the quality of the volcanic activity reports we receive. Reports published in the Bulletin of the Global Volcanism Network are monthly, and more carefully reviewed, although all of the volcanoes discussed in the Weekly Volcanic Activity Report are not necessarily reported in the Bulletin. Because of our emphasis on rapid reporting on the web we have avoided diacritical marks. Reports are updated on the Weekly Volcanic Activity Report web page as they are received, therefore information may be included regarding events that occurred before the current report period.

2. Rapidly developing events lead to coverage that is often fragmentary. Volcanoes, their eruptions, and their plumes and associated atmospheric effects are complex phenomena that may require months to years of data analysis in order to create a comprehensive summary and interpretation of events.

3. Preliminary accounts sometimes contain exaggerations and "false alarms," and accordingly, this report may include some events ultimately found to be erroneous or misleading.

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An RSS (Really Simple Syndication) feed for the Weekly Volcanic Activity Report first made available on 5 March 2008 can be utilized with the aid of various free downloadable readers. The report content of the news feed is identical to the Weekly Volcanic Activity Report minus some features including the header information (latitude and longitude and summit elevation), the Geologic Summary, and a link to the volcano's page from the Global Volcanism Program. Each volcano report includes a link from the volcano's name back to the more complete information in the Weekly Volcanic Activity Report on the Smithsonian website. On 12 March 2009, GeoRSS tags were added so that the latitude and longitude for each volcano could be included with the feed.

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A Google Earth network link for the Weekly Volcanic Activity Report was first made available on 1 April 2009. This file can be loaded into the free Google Earth software, and in turn will load placemarks for volcanoes in the current weekly report. Placemark balloons include the volcano name, report date, report text, sources, and links back to the GVP volcano page for that volcano and to the complete Weekly Report for that week.